The present invention relates to an image processing apparatus, and particularly to an image processing apparatus having an erasure means by which unnecessary image formation about an area outside the document is not conducted.
As the conventional image processing apparatus, for example, a copier by which a reflected light acquired by projecting the light emitted from a light source onto a document placed on, for example, a platen glass is converted (image reading)into an electric signal (document image data) by an electric light conversion element, and by this electric signal, a semiconductor laser is driven and an electrostatic latent image is formed on a photoreceptor, and a toner adhered to the electrostatic latent image is transferred onto a recording material, and the document is copied, is proposed.
In this connection, in the conventional image processing apparatus, as a function relating to the document reading, as disclosed in, for example, Japanese Patent Tokkaihei No. 7-307856 or Tokkaihei NO. 7-111579, a copier having a so-called “outside of the document erasure function” is proposed. This outside of the document erasure function is conceptually a function by which, as shown in FIG. 19, relating a document S placed on the platen glass 11, from the density in an area in which the document S exists (in the drawing, a slanting line portion attached with a mark SR, hereinafter called “document area SR”) and the density in an area in which the document S does not exist (in the drawing, a portion attached with a mark SR, hereinafter called “outside document area NSR”), both area are distinguished, and according to the distinction, relating to the outside document area NSR, the image formation is conducted onto the recording material with white (without transferring the toner).
In this connection, when the outside of the document erasure function is used, in order that the distinction of the document area SR and the outside document area NSR may be more securely conducted, normally, it is made in a condition that a platen cover normally provided so as to cover the platen glass 11 is opened, and relating to the outside document area NSR, it is made in a condition such that the so-called sky shot is conducted. In this connection, the sky shot means that the light is projected to an area in which nothing to reflect the light of the light source exists, and therefore, the reflected light intensity becomes almost zero.
When such the outside of the document erasure function is used, the information relating to a useless area except the document S is not outputted on the recording material (a solid black output according to the sky shot), and the copy processing of the bad appearance is not conducted, and further, the large amount consumption of the toner accompanied by the solid black output can be avoided.
In this connection, the recognition of the “density” to distinguish the document area SR from the outside document area NSR is generally conducted as follows according to the official gazettes. That is, initially, the reflected light and the luminance data as its electric signal are acquired for the first line of the primary scanning direction MS shown together in FIG. 19. This luminance data value is made the binary coded data divided into a document background data value (for example, “1”) relating to the document area SR and a non-document background data value (for example, “0”) relating to the outside document area NSR according to whether it is higher or lower than a threshold level which is a predetermined fixed value. The acquirement of this binary coded data is successively conducted, for example, from the first line on, the first line shown in FIG. 19, . . . , m line, . . . , n line, and a logical sum is acquired for the before data at every time of the data acquirement for each line, and by the logical sum, the binary coded data is successively renewed in a line memory. Then, in the finally acquired binary coded data, the two positions in which the document background data values which are most separated from each other in its primary scanning direction MS exist, are recognized as positions to form the document areas SR in the left and right directions in FIG. 19.
Such a condition is easily understood when, for example, as shown in FIG. 20, the document S0 whose shape is an irregular shape, is presumed. In this drawing, it is found that the document background data value which is confirmed in the most separated position in the primary scanning direction MS is the “1-th line”, and further, the binary coded data acquired at this time point, is, so to call it, “saved” (because the logical sum is conducted) until the final m-th line data in which the document S0 exists is renewed. Accordingly, both end points of the 1-th line are recognized as the points at which they form the document area SR relating to the primary scanning direction MS (refer to a dotted line in FIG. 20).
On the one hand, together with such the recognition processing of the document area SR relating to the primary scanning direction MS, both end positions in the foremost primary scanning line which is recognized that the document background data value exists (the 1-th line in FIGS. 19 and 20) and the secondary scanning direction AS in which the final primary scanning line (similarly, the m-th line in FIGS. 19 and 20) positions, are stored. Then, it is recognized that an area sandwiched by both end positions form the document areas SR in the upper and lower directions in FIGS. 19 and 20 (definite form erasure). Hereinafter, “the definite form erasure” is called “the rectangle erasure”.
Further, as described above, other than a method (the rectangle erasure) by which the area sandwiched by the primary scanning direction MS both end positions and the secondary scanning direction AS both end positions recognizes the document area SR, a method by which, from the binary coded data acquired for each line of the primary scanning direction MS, an area between positions at which the document background data values are most separated on the line of the primary scanning direction MS, is confirmed as the document area SR in the line and this confirmation is conducted for each line and the document area SR is recognized, is also proposed (indefinite form erasure). Hereinafter, the “indefinite form erasure” is called an “oblique angle erasure”. According to this method, even when it is an irregular shaped document as shown in FIG. 20, the document area SR can be recognized. A slanting line portion in FIG. 20 can be recognized as a portion which forms the document area SR.
However, there is a following problem for the above outside of the document erasure function. For example, when the density of the background of the document S is darker, even when the threshold level is set to the darker, when the oblique angle erasure is used, because the density difference between the background of the document S and the outside document area NSR is small, the background of the document S is wrongly recognized as the outside document area NSR, and by the outside of the document erasure, there is a case where the image is cut. In this case, when the rectangle erasure is used, even when it is wrongly recognized at several portions, because there is no case where it is wrongly recognized at all portions, the primary scanning direction MS both end positions and the secondary scanning direction AS both direction positions are recognized, and as a result, there is no case where the image is cut.
However, in the rectangle erasure, for example, 4 triangle portions other than the slanting line portion of an area surrounded among the dotted line showing the primary scanning direction document area in FIG. 20 and an 1 line and an m line, are outputted in the black solid portion (the density of the outside document area). In this case, when the density of the background of the document S is lighter, the image is of bad appearance.
Accordingly, when the failure is generated, because the user of the apparatus repeats changing the outside of the document erasure function setting and re-copying it, the uselessness is generated.
Further, when the threshold level is set to darker, for example, the external light such as the sun light incident from the window or the fluorescent lamp light arranged on the ceiling, is incident onto the image reading section, (for example, ≈255), and thereby, there is a case where the document area SR is erroneously recognized, and there is also a failure in which the unnecessary image which is quite unexpected is formed on the recording material.